The k0-NAA method is known as one of developing Neutron Activation Analysis (NAA) methods that has many advantages. The aim of this work was to validate the k0-NAA method for neutron activation analysis using the Kayzero run under Windows software package at the CAST – NNEA neutron activation analysis laboratory. Three types of reference material from the US National Institute of Standards and Technology were used to determine the precision and accuracy of the k0-NAA method. The samples were irradiated in Kartini reactor at 100 kW of power level. The element content in Standard Reference Materials (SRM) and the statistical evaluation of the experimental results were tested by Utest. The analytical results of the reference materials determined by the k0-NAA method are not significantly different from the certified values. The Utest statistical result, which is to indicate the accuracy, shows that most elements are within 2. It suggests that the k0-NAA method can be successfully applied at the Kartini reactor.